what is the opcode staticcall’s address input in the tornado cash contracts?

the 2nd argument in the staticcalls should be the address of the contract being called.

In the tornado cash contracts, why is the 2nd argument always a digit?
success := staticcall(sub(gas(), 2000), 8, add(input, 0x20), mul(inputSize, 0x20), out, 0x20)